The invention relates to media handling devices. In particular, the invention relates to a protocol for media handoff between devices using either continuous or indexed feed.
For a processing medium such as paper, the medium may be transported through several media handling devices in a media path. Each of the devices in a media path is provided with a media driver such as rollers. Such media handling devices may include printers, fax machines, scanners, or a variety of other such devices. Typically, the devices are placed substantially adjacent to each other in the media path, allowing automatic handoff from the output of one device to the input of the next device.
Typically, media handling devices in a media path process media in a continuous mode. In such a mode, when one device outputs a medium, the next device in the path accepts that output and continues transporting the medium in a continuous manner. Once the second device begins the process of receiving the medium, no further communications are made between the two devices. Thus, the next device continues to process the medium, and no interruptions in the movement of the medium are allowed. An example of a continuous-mode device is a laser printer. Laser printers process a medium as it continuously moves through the device.
However, a media path may contain a device that requires indexed movement, rather than continuous movement. An example of such a device is an ink jet printer. An ink jet printer typically periodically moves the medium a predetermined amount during the printing operation. While the medium is stopped, the ink jet printer prints on a section of the medium before again moving the medium a predetermined amount. Existing media handling systems do not accommodate handoff between two devices in a media path if one or more of the devices requires indexed movement.
During a handoff, the last set of rollers of one device and the first set of rollers of the next device in the media path typically have control of the media simultaneously for at least some period of time. Certain devices may have releasable rollers that can release the medium once the next device has the medium between its rollers. Thus, once the next device has the medium between its rollers, it transports the medium with no assistance from the previous device. Such operation is hereinafter referred to as xe2x80x9cno-assist operationxe2x80x9d.
Certain devices, however, may not have releasable rollers and may maintain some control over the movement of the medium even after the next device has the medium between its rollers. Thus, the medium may simultaneously be under the control of two separate devices. Such operation is hereinafter referred to as xe2x80x9cassisted operationxe2x80x9d.
The invention provides a handoff protocol that is capable of accommodating handoffs requiring indexed feed. In additional embodiments, the invention provides a protocol which also accommodates continuous-feed handoffs and handoffs with no-assist or assist operation.
One embodiment of the invention provides a method of media handoff from a first device to a second device comprising transmitting a first signal from said first device indicating a medium at a predetermined handoff point; receiving a second signal from the second device instructing the first device to transport the medium toward the second device; transporting the medium toward the second device; receiving a third signal from the second device indicating acceptance of the medium by the second device; receiving a fourth signal from the second device instructing the first device to transport the medium a predetermined distance; and transporting the medium the predetermined distance.
According to another embodiment of the invention, a media handoff system comprises a first media handling device comprising a first media driver for transporting a medium through the first media handling device and a first controller for controlling the first media driver; and a second media handling device comprising a second media driver for receiving the medium from the first media handling device and transporting the medium through the second media handling device and a second controller for controlling the second media driver and being adapted to communicate with the first controller; wherein the first controller is adapted to receive signals from the second controller and to start or stop the first media driver in response to the signals.